title: Inhibition of tumour necrosis factor and IL-17 production by leflunomide involves the JAK/STAT pathway.
abstract: OBJECTIVE
  To study the effects of different disease-modifying antirheumatic drugs (DMARD) on different events mediated by IL-15-activated lymphocytes.
  
  
  METHODS
  Peripheral blood lymphocytes (PBL) were isolated from healthy donors and activated with IL-15 after exposure to different DMARD: leflunomide, cyclosporin A, methotrexate, mycophenolic acid, FK-506, sulphasalazine and sodium aurothiomalate. The expression of different surface molecules on the PBL was then determined by flow cytometry. Cells were also co-cultured with the monocytic cell line THP-1 and the tumour necrosis factor (TNF) concentration in the supernatant was measured after 24 h using an immunoenzyme assay. The effect of the aforementioned drugs on IL-17 production by IL-15-activated PBL was also studied.
  
  
  RESULTS
  Treatment of PBL with leflunomide, cyclosporin A and FK-506 inhibited the IL-15-induced expression of both CD54 and CD69 by PBL, as well as TNF production in co-cultures of activated PBL and THP-1 cells. The downregulation of CD54 and CD69 in PBL was correlated with the inhibition of TNF production. Likewise, leflunomide, cyclosporin A and FK-506 all inhibited IL-17 production in IL-15-activated PBL. Interestingly, the effect of leflunomide was not reverted by the presence of uridine in the medium. In addition, leflunomide inhibited the phosphorylation of STAT6 in vitro.
  
  
  CONCLUSIONS
  Inhibition of the JAK/STAT pathway may represent an additional effect of leflunomide in chronic polyarthritis because it impairs certain events that control proinflammatory TNF and IL-17 cytokine production.
authors.affiliation: Rheumatology Unit, Hospital Universitario de la Princesa. Madrid, Spain. isidoro.ga@ser.es
authors.forename: I
authors.initials: I
authors.lastname: González-Alvaro
authors.forename: A M
authors.initials: AM
authors.lastname: Ortiz
authors.forename: C
authors.initials: C
authors.lastname: Domínguez-Jiménez
authors.forename: A
authors.initials: A
authors.lastname: Aragón-Bodi
authors.forename: B
authors.initials: B
authors.lastname: Díaz Sánchez
authors.forename: F
authors.initials: F
authors.lastname: Sánchez-Madrid
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D018501:Antirheumatic Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D019409:Interleukin-15 / Q000276:immunology; D020381:Interleukin-17 / Q000096:biosynthesis*; D007555:Isoxazoles / Q000494:pharmacology*; D037181:Lectins, C-Type; D000077339:Leflunomide; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D050800:STAT6 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D015854:Up-Regulation / Q000187:drug effects; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018501:Antirheumatic Agents; D018799:Intercellular Adhesion Molecule-1; D019409:Interleukin-15; D020381:Interleukin-17; D007555:Isoxazoles; D037181:Lectins, C-Type; D000077339:Leflunomide; D050800:STAT6 Transcription Factor; D014409:Tumor Necrosis Factor-alpha; D000099192:CD69 Antigens; C494101:STAT6 protein, human